1. Field of the Invention
This invention relates to a process of manufacturing sacks from synthetic thermoplastic, and more particularly to a process for manufacturing plastic film sacks that have increased strength and increased resistance to puncture damage.
2. Description of the Prior Art
Plastic sacks are known where a tubular film is formed from a web of plastic film that has its side portions infolded and overlapped and in which the overlapped side portions are adhesively joined by an adhesive seam. Tubular sections are severed from the tubular film, and the tubular sections are provided with bottom seam welds, are filled, and are then provided with top seam welds to close the sack. Before the severed tubular sections are provided with the transversely extending bottom seam welds, they can be provided with gussets, if desired.
If the filled sacks are made from plastic film, they can be damaged as they are loaded, transported and placed into storage because the plastic film forming the walls of the sacks can very easily be torn when the sacks are subjected to rough handling. Damage to the sacks being handled may result in a loss of as much as 50% of their contents.
Other known sacks consist of tubular sections made from a web of oriented plastic material. Such sacks have a high strength so that they are not damaged even by rough handling or by impacts of pointed articles. But sacks made from webs of oriented plastic material have the disadvantage that they have poor welding gualities, so that considerable difficulties are involved in the making of the top and bottom seam welds.
It is an object of the present invention to provide a process for making plastic film sacks that have high strength and that can easily be provided with bottom and top seam welds.